The present invention generally relates to airplane components. More particularly, the present invention relates to a method and apparatus for building airplane components with a combination of metal and composite materials.
In the past, it has been difficult to securely fasten metal and composite materials to create strong, light-weight articles for various purposes. Composite materials, such as fiberglass, generally do not handle bearing loads well, and tend to fail at stress levels unacceptable for traditional mechanical fasteners. In addition, composite materials generally cannot handle concentrated point loads normal to the surface. Compressive point loads tend to cause the composite material to either crush or xe2x80x9ccreep.xe2x80x9d The composite material tends to act like a quasi-fluid over time, similar to an extremely viscous fluid. A fastener applied under pressure, such as a pop-rivet or tightened screw or bolt, will cause the composite material to slowly flow out from under the head of the fastener. As a result of this creeping, the fastener eventually comes loose.
The problem of fastening metal to composite materials is evident in the aviation industry. While airplane designers often favor the use of composite materials over metal, due to their superior rigidity and lower weight, highly engineered composite parts are relatively expensive compared to their metal counterparts. Although there are existing hybrid airplanes and structures used in aviation, they include independent metal and composite structures that are fastened together at a few well-reinforced points to maintain the component positions. For example, existing hybrid airplanes commonly have all-metal wings bolted onto a steel tubular fuselage with a composite covering giving the fuselage an aerodynamic shape, but which does not handle the majority of structural loads. Thus, the steel skeleton and composite covering do not create a coherent structure.
The industry has recently been focused either on improving all-metal airplane designs, or employing all-composite material designs. While the all-composite material designs are theoretically superior to all-metal designs, the comparatively high cost has prevented the proliferation of such designs. Due to the metal/composite material fastening problem, the aviation industry has largely ignored the possibility of combining metal and composite materials to create a coherent structure. However, the combination in a coherent structure would yield a low-cost, much lower weight airplane with fewer parts than all-metal designs.
Thus, a need exists for a way to securely fasten metal and composite materials together cost effectively to produce a coherent hybrid structure.
Briefly, the present invention satisfies the need for a way to securely fasten metal and composite materials cost effectively by embedding in the composite material a high load bearing strength inlay, relative to the composite material, to transfer a structural load from a fastener coupled to the inlay and distribute it over a wide enough area to reduce or eliminate damage to the composite material from the applied load.
In accordance with the above, it is an object of the present invention to provide a way to securely fasten metal and composite materials to form a coherent structure.
It is another object of the present invention to provide a cost-effective way to securely fasten metal and composite materials to form a coherent structure.
The present invention provides, in a first aspect, an airplane component, comprising a metal frame and a skin of composite material fastened to the metal frame. The skin is adapted to transfer a structural load when applied thereto.
The present invention provides, in a second aspect, a method of building an airplane component, comprising adapting a composite material airplane skin to transfer a structural load when applied thereto, and fastening the adapted composite material airplane skin to a metal airplane frame.
These, and other objects, features and advantages of this invention will become apparent from the following detailed description of the various aspects of the invention taken in conjunction with the accompanying drawings.